The aim of the research is to understand how the information encoded on the DNA specifies temporal, spatial, and quantitative patterns of control in the expression of eukaryotic genes. We propose two different strategies to approach this problem. The first one involves the use of "reverse genetics" to identify transcriptional regulatory sequences involved in the control of the expression of the Drosophila hsp28 gene, both by heat shock and by ecdysone. We will use P element-mediated transformation of Drosophila embryos to analyze the effect of in vitro-constructed external deletions, linker-scanning mutants and point mutations on the transcription of hsp28 and its developmental and tissue-specific patterns of expression. These effects on transcription will be correlated with specific chromatin changes in the regions adjacent to the gene. The second approach involves the molecular analysis of the DNA lesions that cause mutant phenotypes at the forked and yellow loci of Drosophila. DNA sequences defining these genes will be cloned from specific mutant alleles which have a particularly interesting phenotype affecting the levels or tissue-specific expression of the RNAs encoded by these loci. From the correlation between the molecular lesion and the particular phenotype, we will be able to assign functional roles to different DNA sequences involved in control of transcription.